Millimeter wave signals are used for radar and telecommunications. They are also capable of being used to produce data representative of a subject, by directing millimeter-wave signals at the subject and detecting the reflected signal. The data produced may then be used to produce an image of the subject. Examples of such imaging systems are described in U.S. Pat. Nos. 5,455,590; 5,557,283; 5,859,609; 6,507,309; and 6,703,964; and U.S. Patent Publication Nos. 2004/90,359; 2004/140,924; and 2004/263,379, which patent references are incorporated herein by reference.